Jackson is 1-7 in his last eight decisions with a 8.92 ERA in those games. Manager Rick Renteria was tightlipped about what could be next for him, noting command was the biggest issue.

"We're going to assess and evaluate and see where we go," Renteria said.

Before the game, the Giants won their protest filed with Major League Baseball over Tuesday night's rain-shortened loss that was called in the fifth inning. A problem in getting the tarp onto the field caused unplayable conditions, and the game was ruled a 2-0 Cubs win after a delay of 4 1-2 hours.

"We may win it. We may lose it, but at least we're going to finish the game and at this stage I think that's the right thing to do," Giants manager Bruce Bochy said.

MLB ruled the tarp hadn't been properly put away after its previous use, and therefore there was a "malfunction of a mechanical field device under control of the home club."

Peavy has won two straight after losing his first three starts with San Francisco following a July 26 trade from Boston, where he was 1-9. He allowed 10 hits, struck out eight and walked none. Chris Valaika's homer in the second inning accounted for the only runs against him.

Hunter Pence and Andrew Susac homered, and Travis Ishikawa drove in three runs with pair of doubles among three hits.

Luis Valbuena homered, tripled and singled for Chicago, which hit into three double plays to scuttle early opportunities.

The Giants jumped out to a 4-0 lead in the first inning as five of their first six batters reached base. Ishikawa drove in two runs with his first double to cap the outburst.

Ishikawa doubled in another run in the third and scored on Susac's first career homer as San Francisco opened a 7-2 lead.

Pence led off the fourth against Carlos Villenueva with his 17th homer of this season to make it 8-2.

UP NEXT

The suspended game will resume on Thursday with the Cubs batting in the bottom of the 5th inning and leading 2-0 against RHP Yusmeiro Petit (3-3, 3.89 ERA). RHP Jacob Turner (4-7, 5.80) will resume action for Chicago. In the regularly scheduled game, Giants LHP Madison Bumgarner (13-9, 3.14) is set to face LHP Travis Wood (7-10, 4.86).

TRAINER'S ROOM

Giants: C Buster Posey was out of the lineup because of soreness in his left hip. Bochy likened it to an unscheduled day off, and expected Posey to be back behind the plate on Thursday.

Cubs: SS Starlin Castro was a last-minute scratch from the lineup due to a family emergency. The team didn't specify, but said he would likely be placed on the bereavement list. ... LHP Felix Doubront, placed on the DL with a left calf strain on Aug. 1, threw on the side on Wednesday. He is expected to make another rehab start at Double-A Tennessee on Sunday or Monday. Renteria said Doubront, acquired from Boston on July 30, is in line to be recalled and start on Aug. 30 when the Cubs play a doubleheader at St. Louis.